Ear infections are among the most common reasons for sick child visits to medical providers. Risk factors for otitis media have been identified in prior clinical studies, but epidemiologic studies of sufficient size to allow generalization to the wider community or national population have been less common. Our goal has been to extend this research by analyzing several U.S. national data sets, collected under the auspices of the National Center for Health Statistics, with support from NIH, and other available population-based datasets. A paper was published this year on the prevalence and risk factors for placement of tympanostomy ear tubes in U.S. children. We have also examined recent trends in physician office, emergency room, and hospital visits for otitis media and treatments in the U.S., and analyzed data from the Third National Health and Nutrition Examination Survey (NHANES III). Findings of these and other studies were presented at the Seventh International Symposium on Recent Advances in Otitis Media (OM) in Ft. Lauderdale, FL, last summer and will be published in the Proceedings. Using four yearly surveys, the National Ambulatory Medical Care Survey, the National Hospital Ambulatory Medical Care Survey, the National Survey of Ambulatory Surgery, and the National Hospital Discharge Survey, we have been able to assess the burden of disease due to OM in recent years in the U.S. Using 1996 data, we found a national rate of OM of 40 visits per 100 children under the age of 15 years, or 33 visits per 100 children if restricted to physician offices only. Hispanic children under the age of 6 were more likely to be diagnosed with OM compared to non-Hispanic white or black children. Also, children in the West were more likely to be diagnosed with OM than children from other regions of the U.S. However, this higher prevalence of diagnosis did not translate into higher rates of surgical intervention with myringotomy and tube placement. Instead, the South had the highest rate of tube placement. In NHANES III and other studies, for example, the Children in Focus sample of the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC), we have studied the prevalence of otitis media with effusion (OME) based on published criteria for "flat" tympanograms. We have correlated results of hearing exams and other developmental outcomes for children with OME and presented this information at the OM meetings as well. In addition, we have examined outcomes at age 5 for children with otitis media from a longitudinal study, the Scandinavian Successive Small-for-Gestational Age Birth Study. This study provides further support for poorer developmental outcomes of children with frequent ear infections early in childhood and for those with fluctuating hearing loss associated with OME. This study, based on middle-income families in Norway and Sweden with universal access to health care, suggests that even among these relatively advantaged children important differences in developmental outcomes are found, especially for children with fluctuating hearing loss in early childhood.